U.S. patent application number 11/125657 was filed with the patent office on 2005-09-29 for methods for preparing polymers in carbon dioxide having reactive functionality.
This patent application is currently assigned to North Carolina State University. Invention is credited to DeSimone, Joseph M., Young, Jennifer L..
Application Number | 20050215746 11/125657 |
Document ID | / |
Family ID | 24752083 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050215746 |
Kind Code |
A1 |
DeSimone, Joseph M. ; et
al. |
September 29, 2005 |
Methods for preparing polymers in carbon dioxide having reactive
functionality
Abstract
A method of forming a polymer having reactive functionality
comprises providing a reaction mixture comprising at least one
monomer having at least one reactive functional group and carbon
dioxide; and polymerizing the at least one monomer in the reaction
mixture to form a polymer having reactive functionality associated
with the at least one reactive functional group.
Inventors: |
DeSimone, Joseph M.; (Chapel
Hill, NC) ; Young, Jennifer L.; (Wilmington,
DE) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Assignee: |
North Carolina State
University
The University of North Carolina at Chapel Hill
|
Family ID: |
24752083 |
Appl. No.: |
11/125657 |
Filed: |
May 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11125657 |
May 10, 2005 |
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09971552 |
Oct 4, 2001 |
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09971552 |
Oct 4, 2001 |
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09685409 |
Oct 9, 2000 |
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Current U.S.
Class: |
528/12 ; 526/942;
528/222; 528/271; 528/421; 528/422; 528/44 |
Current CPC
Class: |
C08F 220/36 20130101;
C08F 212/08 20130101; C08F 220/14 20130101; C08G 83/00 20130101;
C08F 2/04 20130101; C08F 220/325 20200201; C08F 220/14 20130101;
C08G 18/0847 20130101; C08F 265/06 20130101; C08G 18/8175 20130101;
C08G 18/728 20130101; C08F 265/04 20130101; C08F 220/36 20130101;
C08F 265/04 20130101 |
Class at
Publication: |
526/942 ;
528/012; 528/421; 528/044; 528/222; 528/271; 528/422 |
International
Class: |
C08G 085/00 |
Claims
1. A method of forming a polymer having reactive functionality,
said method comprising: providing a reaction mixture comprising at
least one monomer having at least one reactive functional group and
carbon dioxide; and polymerizing the at least one monomer in the
reaction mixture to form a polymer having reactive functionality
associated with the at least one reactive functional group.
2. The method according to claim 1, wherein the at least one
monomer further includes at least one vinyl group, and the reaction
mixture further comprises an initiator.
3. The method according to claim 1, wherein the carbon dioxide is
liquid carbon dioxide.
4. The method according to claim 1, wherein the carbon dioxide is
supercritical carbon dioxide.
5. The method according to claim 1, wherein at least one monomer is
an isocyanate-containing monomer.
6. The method according to claim 1, wherein the at least one
monomer is an epoxy-containing monomer.
7. The method according to claim 1, wherein the at least one
monomer is a ketone-containing monomer.
8. The method according to claim 1, wherein the at least one
monomer is an amide-containing monomer.
9. The method according to claim 1, wherein the at least one
monomer is a carboxylic acid-containing monomer.
10. The method according to claim 1, wherein the at least one
monomer is an acid halide-containing monomer.
11. The method according to claim 1, wherein the at least one
monomer is an acetoxy-containing monomer.
12. The method according to claim 1, wherein the at least one
monomer is an alkoxy silane-containing monomer.
13. The method according to claim 1, wherein the at least one
monomer is a silyl halide-containing monomer.
14. The method according to claim 1, wherein the at least one
monomer is an anhydride-containing monomer.
15. The method according to claim 1, wherein the at least one
monomer is melamine.
16. The method according to claim 1, wherein the at least one
monomer is an aldehyde-containing monomer.
17. The method according to claim 2, wherein the initiator is
selected from the group consisting of acetylcyclohexanesulfonyl
peroxide; diacetyl peroxydicarbonate; dicyclohexyl
peroxydicarbonate; di-2-ethylhexyl peroxydicarbonate; tert-butyl
perneodecanoate; 2,2'-azobis (methoxy-2,4-dimethylvaleronitrile;
tert-butyl perpivalate; dioctanoyl peroxide; dilauroyl peroxide;
2,2'-azobis (2,4-dimethylvaleronitrile);
tert-butylazo-2-cyanobutane; dibenzoyl peroxide; tert-butyl
per-2-ethylhexanoate; tert-butyl permaleate; 2,2-azobis
(isobutyronitrile); bis(tert-butylperoxy) cyclohexane; tert-butyl
peroxyisopropylcarbonate; tert-butyl peracetate; 2,2-bis
(tert-butylperoxy) butane; dicumyl peroxide; ditertamyl peroxide;
di-tert-butyl peroxide; p-methane hydroperoxide; pinane
hydroperoxide; cumene hydroperoxide; tert-butyl hydroperoxide; and
mixtures thereof.
18. The method according to claim 2, wherein the initiator is
azobisisobutyronitrile.
19. The method according to claim 1, wherein the reaction mixture
comprises at least one additional monomer, and wherein said
polymerizing step comprises polymerizing the at least one monomer
having at least one reactive functional group with at least one
additional monomer to form a copolymer.
20. The method according to claim 19, wherein the at least one
additional monomer is selected from the group consisting of an
ester monomer, vinyl chloride, vinyl acetate, ethylene,
acrylonitrile, maleic anhydride, a diene, an aromatic monomer, a
monomer that provides crosslinking and branching, and mixtures
thereof.
21. The method according to claim 19, wherein the at least one
additional monomer is a fluoromonomer.
22. The method according to claim 21, wherein the fluoromonomer is
selected from the group consisting of tetrafluoroethylene;
CF.sub.2.dbd.CFR.sub.f, where R.sub.f is a perfluoroalkyl group
having 1 to 10 carbon atoms, perfluoro(alkyl vinyl ethers),
chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride,
fluorinated dioxoles, fluorinated alkenyl vinyl ethers, and
mixtures thereof.
23. The method according to claim 21, wherein the fluoromonomer is
selected from the group consisting of
CF.sub.2CF(CF.sub.3)--O--CF.sub.2CF- .sub.2CO.sub.2CH.sub.3,
CF.sub.2.dbd.CF--O--CF.sub.2CF.sub.2CO.sub.2CH.sub- .3,
CF.sub.2.dbd.CF--O--(CF.sub.2).sub.n--CF.dbd.CF.sub.2 wherein n is
1 or 2,
CF.sub.2.dbd.CF--(O--CF.sub.2CFR.sub.f).sub.a-O--CF.sub.2CFR'.sub.f-
SO.sub.2F wherein R.sub.f and R'.sub.f are independently selected
from F, Cl or a perfluorinated alkyl group having 1 to 10 carbon
atoms, a is 1 or 2,
CF.sub.2.dbd.CF--(O--CF.sub.2CFR.sub.f).sub.a-O--CF.sub.2CFR'.sub.fCO.-
sub.2CH.sub.3 wherein R.sub.f and R'.sub.f are independently
selected from F, Cl or a perfluorinated alkyl group having 1 to 10
carbon atoms, a is 0, 1 or 2, and mixtures thereof.
24. The method according to claim 21, wherein the reaction mixture
further comprises a third monomer which copolymerizes with the at
least one monomer having at least one reactive functional group and
the fluoromonomer.
25. The method according to claim 24, wherein the third monomer is
selected from the group consisting of an ester monomer, vinyl
chloride, vinyl acetate, ethylene, acrylonitrile, maleic anhydride,
a diene, an aromatic monomer, a monomer that provides crosslinking
and branching, and mixtures thereof.
26. The method according to claim 24, wherein the third monomer is
selected from the group consisting of perfluoroalkylethylenes,
ethylene, propylene, and mixtures thereof.
27. The method according to claim 21, wherein the initiator is a
halogented initiator which is a perhalogenated initiator selected
from the group consisting of perchlorinated initiators and
perfluorinated initiators.
28. The method according to claim 25, wherein the initiator is a
perfluorinated initiator of the formula:
Rf--(C.dbd.O)--O--O--(C.dbd.O)-R- .sub.f wherein R.sub.f is a
perfluoroalkyl group of 1 to 8 carbon atoms that may contain from 0
to 4 ether linkages.
29. The method according to claim 27, wherein the perfluorinated
initiator is selected from the group consisting of
perfluoropropionyl peroxide and
CF.sub.3CF.sub.2CF.sub.2OCF(CF.sub.3)(C.dbd.O)OO(C.dbd.O)(CF.sub.3)CFOCF.-
sub.2CF.sub.2CF.sub.3.
30. The method according to claim 1, further comprising the step of
reacting the polymer containing reactive functionality with a
second polymer containing reactive functionality such that the
polymers containing reactive functionality become crosslinked.
31. The method according to claim 29, wherein the second polymer
containing reactive functionality is selected from the group
consisting of an alcohol, a primary amine, a secondary amine, and
an alkyl halide.
32. The method according to claim 1, further comprising the step of
separating the polymer containing reactive functionality from the
reaction mixture.
33. The method according to claim 32, wherein subsequent to said
step of separating the polymer containing reactive functionality
from the reaction mixture, said method further comprises the step
of applying the polymer containing reactive functionality to a
substrate.
34. The method according to claim 33, wherein said step of applying
the polymer having reactive functionality comprises applying the
polymer with a second polymer containing reactive functionality,
and wherein the polymers containing reactive functionality become
crosslinked.
35. The method according to claim 1, wherein the reaction mixture
further comprises a surfactant.
36. The method according to claim 35, wherein the surfactant
comprises a CO.sub.2-philic segment.
37. The method according to claim 36, wherein the CO.sub.2-philic
segment comprises a fluoropolymer or a siloxane-containing
segment.
38. The method according to claim 36, wherein the surfactant
comprises a CO.sub.2-phobic segment.
39. The method according to claim 1, wherein the polymer having
reactive functionality is present as a solid particle.
40. The method according to claim 39, further comprising the step
of polymerizing at least one additional monomer having ethylenic
unsaturation in the presence of the solid particle to form a second
polymer that becomes attached to the solid particle to form a
composite particle.
41. The method according to claim 40, wherein the at least one
additional monomer is selected from the group consisting of an
ester monomer, vinyl chloride, vinyl acetate, ethylene,
acrylonitrile, maleic anhydride, a diene, a monomer that provides
crosslinking and branching, and mixtures thereof.
42. The method according to claim 1, further comprising the step of
reacting the polymer having reactive functionality with a molecule
containing at least one reactive functional group.
43. The method according to claim 42, wherein the molecule
containing at least one reactive functional group is selected from
the group consisting of an alcohol, a secondary amine, an alkyl
halide, an amino acid, a peptide, an enzyme, a protein, and
combinations thereof.
44-72. (canceled)
Description
CLAIM FOR PRIORITY AND CROSS-REFERENCE TO OTHER APPLICATIONS
[0001] This application claims priority to and is a continuation of
parent application Ser. No. 09/971,552, filed Oct. 4, 2001, which
is a continuation-in-part of parent application Ser. No.
09/685,409, filed Oct. 9, 2000, the disclosures of which are hereby
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention generally relates to processes for preparing
polymers in carbon dioxide.
BACKGROUND OF THE INVENTION
[0003] Highly reactive monomers, for example isocyanates, are often
useful as modifiers for a number of polymers employed in various
applications, particularly coatings and adhesive applications. As
an example, isocyanates having vinyl groups are especially useful.
In particular, the isocyanate group often serves as the site for
chemical modification or grafting to yield a macromonomer and the
vinyl group is employed for polymerization. See e.g. Levesque, G.,
et al., Polymer 1988, 29, pp. 2271-2276 and Liu, Q., et al., J.
Biomed. Mater. Res. 1998, 40, pp. 257-263. Such monomers may also
be copolymerized with other olefinically unsaturated monomers.
[0004] From a processing perspective, polymerizing highly reactive
monomers (e.g., isocyanate monomers) is often difficult since they
are typically highly reactive with water and alcohols. Suspension
polymerizations involving isocyanate monomers have been conducted
in perfluorocarbon solvents. See e.g., Zhu, D-W, Polymer Preprints
1995, 36, pp. 249-250 and Zhu, D-W, Macromolecules 1996, 29, pp.
2813-2817. Notwithstanding any developments, there remains a need
in the art for polymerization processes involving reactive monomers
that may be carried out in a potentially more environmentally
benign media.
SUMMARY OF THE INVENTION
[0005] In one aspect, the invention relates to a method of forming
a polymer having reactive functionality. The method comprises
providing a reaction mixture comprising at least one monomer having
at least one reactive functional group and carbon dioxide; and
polymerizing the at least one monomer in the reaction mixture to
form a polymer having reactive functionality associated with the at
least one reactive functional group.
[0006] These and other aspects and advantages are provided by the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0007] The present invention now will be described more fully
hereinafter with reference to the accompanying specification and
examples, in which preferred embodiments of the invention are
shown. This invention may, however, be embodied in many different
forms and should not be construed as limited to the embodiments set
forth herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art.
[0008] In one aspect, the invention relates to a method of forming
a polymer having reactive functionality. The method comprises
providing a reaction mixture comprising at least one monomer having
at least one reactive functional group and carbon dioxide; and
polymerizing the at least one monomer in the reaction mixture
(e.g., carbon dioxide) to form a polymer having reactive
functionality associated with the at least one reactive functional
group. In a preferred embodiment, the monomer has at least one
vinyl group, and an initiator is present in the reaction
mixture.
[0009] For the purposes of the invention the term "reactive
functional group" may be defined as an electrophilic functional
group susceptible to reaction with a nucleophile. Various reactive
functional groups include, without limitation, isocyanate, epoxy,
aldehyde, carboxylic acid, acid halide, acetoxy, alkoxy silane,
silyl halide, anhydride, ketone, amide, and melamine. In general,
the monomers, without limitation, are olefinically unsaturated
monomers that contain at least one pendant reactive functional
group described hereinabove. Various monomers include, without
limitation, isocyanate-containing monomers (e.g., isocyanatoethyl
methacrylate and .alpha., .alpha.-dimethyl-3-isopropenyl benzyl
isocyanate), epoxy-containing monomers (e.g., glycidyl acrylate,
glycidyl methacrylate and allyl glycidyl ether),
aldehyde-containing monomers (e.g., acrolein and methacrolein),
ketone-containing monomers (e.g., vinyl methyl ketone and methyl
isopropenyl ketone), amide-containing monomers (e.g. acrylamide and
methacrylamide), carboxylic acid-containing monomers (e.g., acrylic
acid and methacrylic acid), acid halide-containing monomers (e.g.,
acryloyl chloride and methacryloyl chloride), acetoxy-containing
monomers (e.g. 2-(methacryloyloxy)ethyl acetoacetate), alkoxy
silane-containing monomers (e.g. 3-(trimethoxysilyl)propyl
methacrylate and 3-(triethoxysilyl)propyl acrylate) silyl
halide-containing monomers (e.g. 3-(chlorodimethylsilyl)p- ropyl
methacrylate) anhydride-containing monomers (e.g. acrylic
anhydride, maleic anhydride), and melamine.
[0010] In one embodiment, it is preferred to use monomers
containing isocyanate functionality. Exemplary monomers of this
type include, without limitation, 2-isocyanatoethyl methacrylate,
and .alpha., .alpha.-dimethyl-3-isopropenyl benzyl isocyanate.
[0011] The monomers may be used in various amounts relative to the
carbon dioxide. For the purposes of the invention, the monomers
preferably are employed in an amount ranging from about 1, 10, or
20 to about 50, 60, or 70 percent based on the weight of the carbon
dioxide, and more preferably from about 5 percent to about 30
percent.
[0012] For the purposes of the invention, the term "polymer" is to
be broadly construed to mean homopolymer, copolymer, terpolymer, or
the like. Accordingly, the monomer may be polymerized to form a
homopolymer, or alternatively may be polymerized with at least one
additional monomer to form a copolymer (e.g., block, random, graft,
or others), terpolymer, and the like. Examples of suitable
additional monomers are those that are olefinically unsaturated and
include, without limitation, ester monomers (e.g., methyl acrylate,
methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl
acrylate, butyl methacrylate, 2-ethylhexyl acrylate, isobutyl
methacrylate, and n-propyl methacrylate), vinyl chloride, vinyl
acetate, ethylene, acrylonitrile, maleic anhydride, dienes (e.g.,
isoprene, chloroprene, and butadiene), aromatic monomers (e.g.,
styrene, alpha-methyl styrene, p-methyl styrene, vinyl toluene,
ethylstyrene, tert-butyl styrene, monochlorostyrene,
dichlorostyrene, vinyl benzyl chloride, vinyl pyridine, vinyl
naphthalene, fluorostyrene, and alkoxystyrenes (e.g.,
p-methoxystyrene)), and monomers that provide cross-linking and
branching (e.g., divinyl benzene and di- and triacrylates).
[0013] Other additional monomers that may be employed include,
without limitation, fluoromonomers such that polymers (e.g.,
copolymers) are formed by virtue of the method of the invention
that have reactive functionality. Exemplary fluoromonomers include,
but are not limited to, tetrafluoroethylene (TFE);
CF.sub.2.dbd.CFR.sub.f, where R.sub.f is a perfluoroalkyl group
having 1 to 10 carbon atoms, preferably hexafluoropropylene (HFP);
perfluoro(alkyl vinyl ethers) (PAVE) wherein the alkyl group has
from 1 to 10 carbon atoms and may include ether linkages;
chlorotrifluoroethylene (CTFE); vinylidene fluoride (VF.sub.2);
vinyl fluoride (VF); fluorinated dioxoles such as
perfluoro-2-methylene-4- -methyl-1,3-dioxole and preferably
perfluoro(2,2,-dimethyl-1,3-dioxole); fluorinated alkenyl vinyl
ethers such as:
[0014] CF.sub.2.dbd.CF--O--(CF.sub.2).sub.n--CF.dbd.CF.sub.2,
wherein n is 1 or 2;
[0015]
CF.sub.2.dbd.CF--(O--CF.sub.2CFR.sub.f).sub.a-O--CF.sub.2CFR'.sub.f-
SO.sub.2F wherein R.sub.f and R'.sub.f are independently selected
from F, Cl or a perfluorinated alkyl group having 1 to 10 carbon
atoms, a is 0, 1 or 2, preferably
CF.sub.2.dbd.CF--O--CF.sub.2CF(CF.sub.3)-O-CF.sub.2CF.su-
b.2SO.sub.2F (perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl
fluoride)) and CF.sub.2.dbd.CF--O--CF.sub.2CF.sub.2SO.sub.2F
(perfluoro(3-oxa-4-pentenes- ulfonyl fluoride)); and
CF.sub.2.dbd.CF--(O--CF.sub.2CFR.sub.f).sub.a--O---
CF.sub.2CFR'.sub.fCO.sub.2CH.sub.3 wherein R.sub.f and R'.sub.f are
independently selected from F, Cl or a perfluorinated alkyl group
having 1 to 10 carbon atoms, a is 0, 1 or 2, preferably
CF.sub.2.dbd.CF--O--CF.s-
ub.2CF(CF.sub.3)--O--CF.sub.2CF.sub.2CO.sub.2CH.sub.3 and
CF.sub.2.dbd.CF--O--CF.sub.2CF.sub.2CO.sub.2CH.sub.3.
Perfluoroalkylethylenes such as C.sub.4F.sub.9--CH.dbd.CH.sub.2 as
well as ethylene and/or propylene are suitable comonomers when the
above fluoromonomers may also be used.
[0016] In embodiments encompassing the polymerization of
fluoromonomers, particularly in embodiments encompassing
perfluoropolymers, halogenated initiators are preferred. Exemplary
initiators are perhalogenated initiators, more preferably
perchlorinated initiators, and most preferably perfluorinated
initiators. An example of a preferred group of perfluorinated
initiators is:
[0017] R.sub.f--(C.dbd.O)--O--O--(C.dbd.O)-R.sub.f, where R.sub.f
is a perfluoroalkyl group of 1 to 8 carbon atoms that may contain 0
to 4 ether linkages. Preferred examples are perfluoropropionyl
peroxide also known as "3P", and
CF.sub.3CF.sub.2CF.sub.2OCF(CF.sub.3)(C.dbd.O)OO(C.dbd.O)(CF-
.sub.3)CFOCF.sub.2CF.sub.2CF.sub.3, also known as HFPO dimer
peroxide.
[0018] Mixtures of these monomers can also be employed. Other
comonomers, without limitation, include the reactive functional
monomers listed hereinabove as long as the comonomers used in the
copolymerization do not react with each other.
[0019] The above olefinically unsaturated comonomer can be used in
various amounts. If employed, the reaction mixture preferably
comprises from about 1 to about 99 percent by weight of the
olefinically unsaturated comonomer based on the weight of the
reactive functional monomer.
[0020] For the purposes of the invention, the term "polymer having
reactive functionality" refers to a polymer (e.g., homopolymer,
copolymer, terpolymer, etc.) that has at least one functional group
as defined hereinabove. In a preferred embodiment, the resulting
polymer may be present in the form of a particle. In these
instances, the polymer typically has a diameter ranging from about
0.05 .mu.m to about 10 .mu.m.
[0021] In addition, a third monomer may be employed which
polymerizes with the at least one monomer having at least one
reactive functional group and the additional monomer. Accordingly,
in one embodiment, the method of the invention comprises
copolymerizing the third monomer with the at least one monomer
having at least one reactive functional group and the additional
monomer. In one preferred embodiment, the additional monomer is a
fluoromonomer. A number of monomers may be employed for the third
monomer. Exemplary monomers include, without limitation, ester
monomers (e.g., methyl acrylate, methyl methacrylate, ethyl
acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate,
2-ethylhexyl acrylate, isobutyl methacrylate, and n-propyl
methacrylate), vinyl chloride, vinyl acetate, ethylene,
acrylonitrile, maleic anhydride, dienes (e.g., isoprene,
chloroprene, and butadiene), aromatic monomers (e.g., styrene,
alpha-methyl styrene, p-methyl styrene, vinyl toluene,
ethylstyrene, tert-butyl styrene, monochlorostyrene,
dichlorostyrene, vinyl benzyl chloride, vinyl pyridine, vinyl
naphthalene, fluorostyrene, and alkoxystyrenes (e.g.,
p-methoxystyrene)), and monomers that provide cross-linking and
branching (e.g., divinyl benzene and di- and triacrylates).
Particularly preferred third monomers are perfluoroalkylethylenes,
ethylene, propylene, and mixtures thereof.
[0022] For the purposes of the invention, carbon dioxide is
employed in a liquid or supercritical phase. The reaction mixture
typically employs carbon dioxide as a continuous phase, with the
reaction mixture (initiator, monomer, and other optional
components) typically comprising from about 1 to about 80 percent
by weight of carbon dioxide. If liquid CO.sub.2 is used, the
temperature employed during the process is preferably below
31.degree. C. In one preferred embodiment, the CO.sub.2 is utilized
in a "supercritical" phase. As used herein, "supercritical" means
that a fluid medium is at a temperature that is sufficiently high
that it cannot be liquefied by pressure. The thermodynamic
properties of CO.sub.2 are reported in Hyatt, J. Org. Chem. 49:
5097-5101 (1984); therein, it is stated that the critical
temperature of CO.sub.2 is about 31.degree. C. In particular, the
methods of the present invention are preferably carried out at a
temperature range from about -20.degree. C. to about 100.degree. C.
The pressures employed preferably range from about 200 psia (1.4
MPa) to about 10,000 psia (69 MPa).
[0023] Initiators that may be used in the method of the invention
are numerous and known to those skilled in the art. Examples of
initiators are set forth in U.S. Pat. No. 5,506,317 to DeSimone et
al., the disclosure of which is incorporated by reference herein in
its entirety. Organic free radical initiators are preferred and
include, but are not limited to, the following:
[0024] acetylcyclohexanesulfonyl peroxide; diacetyl
peroxydicarbonate; dicyclohexyl peroxydicarbonate; di-2-ethylhexyl
peroxydicarbonate; tert-butyl perneodecanote,
2,2'-azobis(methoxy-2,4-dimethylvaleronitrile)- ; tert-butyl
perpivalate; dioctanoyl peroxide; dilauroyl peroxide;
2,2'-azobis(2,4-dimethylvaleronitrile);
tert-butylazo-2-cyanobutane; dibenzoyl peroxide; tert-butyl
per-2-ethylhexanoate; tert-butyl permaleate;
2,2-azobis(isobutyronitrile); bis(tert-butylperoxy) cyclohexane;
tert-butyl peroxyisopropylcarbonate; tert-butyl peracetate;
2,2-bis(tert-butylperoxy) butane; dicumyl peroxide; ditert-amyl
peroxide; di-tert-butyl peroxide; p-methane hydroperoxide; pinane
hydroperoxide; cumene hydroperoxide; and tert-butyl hydroperoxide.
Combinations of any of the above initiators can also be used.
Preferably, the initiator is azobis(isobutyronitrile) ("AIBN").
[0025] The initiator may be used in varying amounts. Preferably,
the reaction mixture comprises from about 0.001 to about 20 percent
initiator by weight of the total reaction mixture (e.g., the
homogeneous mixture).
[0026] Optionally, the reaction mixture of the invention may
include a surfactant known to those skilled in the art. Preferably,
the surfactants are non-ionic surfactants. Examples of suitable
surfactants are set forth in U.S. Pat. Nos. 5,783,082; 5,589,105;
5,639,836; and 5,451,633 to DeSimone et al.; U.S. Pat. No.
5,676,705; and 5,683,977 to Jureller et al., the disclosures of
which are incorporated herein by reference in their entirety. In
general, the surfactant may encompass any macromolecule that serves
to emulsify, and may be polymeric or non-polymeric.
[0027] Preferably, the surfactant has a segment that has an
affinity for the material it comes in contact with, or, stated
differently, a "CO.sub.2-phobic segment". Exemplary CO.sub.2-phobic
segments may comprise common lipophilic, oleophilic, and aromatic
polymers, as well as oligomers formed from monomers such as
ethylene, a-olefins, styrenics, acrylates, methacrylates, ethylene
oxides, isobutylene, vinyl alcohols, acrylic acid, methacrylic
acid, and vinyl pyrrolidone. The CO.sub.2-phobic segment may also
comprise molecular units containing various functional groups such
as amides; esters; sulfones; sulfonamides; imides; thiols;
alcohols; dienes; diols; acids such as carboxylic, sulfonic, and
phosphoric; salts of various acids; ethers; ketones; cyanos;
amines; quaternary ammonium salts; and thiozoles. Mixtures of any
of these components can make up the "CO.sub.2-phobic segment". If
desired, the surfactant may comprise a plurality of
"CO.sub.2-phobic" segments. The CO.sub.2-phobic segment preferably
will not contain a functional group that will react with the
reactive functional group of the olefinically unsaturated
monomer.
[0028] If desired, the surfactant may comprise a segment that has
an affinity for carbon dioxide, or a "CO.sub.2-philic" segment.
Exemplary CO.sub.2-philic segments may include a halogen (e.g.,
fluoro or chloro)-containing segment, a siloxane-containing
segment, a branched polyalkylene oxide segment, or mixtures
thereof. Examples of "CO.sub.2-philic" segments are set forth in
U.S. Pat. Nos. 5,676,705; and 5,683,977 to Jureller et al., as well
as U.S. Pat. Nos. 5,783,082; 5,589,105; 5,639,836; and 5,451,633 to
DeSimone et al. If employed, the fluorine-containing segment is
typically a "fluoropolymer". As used herein, a "fluoropolymer" has
its conventional meaning in the art and should also be understood
to include low molecular weight oligomers, i.e., those which have a
degree of polymerization greater than or equal to two. See
generally Banks et al., Organofluorine Compounds: Principals and
Applications (1994); see also Fluorine-Containing Polymers, 7
Encyclopedia of Polymer Science and Engineering 256 (H. Mark et al.
Eds. 2d Ed. 1985). Exemplary fluoropolymers are formed from
monomers which may include fluoroacrylate monomers such as
2-(N-ethylperfluorooctane-sulfona- mido) ethyl acrylate
("EtFOSEA"), 2-(N-ethylperfluorooctane-sulfonamido) ethyl
methacrylate ("EtFOSEMA"), 2-(N-methylperfluorooctane-sulfonamido)
ethyl acrylate ("MeFOSEA"), 2-(N-methylperfluorooctane-sulfonamido)
ethyl methacrylate ("MeFOSEMA"), 1,1'-dihydroperfluorooctyl
acrylate ("FOA"), 1,1'-dihydroperfluorooctyl methacrylate ("FOMA"),
1,1',2,2'-tetrahydroper- fluoroalkylacrylate,
1,1',2,2'-tetrahydroperfluoroalkyl-methacrylate and other
fluoromethacrylates; fluorostyrene monomers such as a-fluorostyrene
and 2,4,6-trifluoromethylstyrene; fluoroalkylene oxide monomers
such as hexafluoropropylene oxide and perfluorocyclohexane oxide;
fluoroolefins such as tetrafluoroethylene, vinylidine fluoride, and
chlorotrifluoroethylene; and fluorinated alkyl vinyl ether monomers
such as perfluoro(propyl vinyl ether) and perfluoro(methyl vinyl
ether). Copolymers using the above monomers may also be employed.
Exemplary siloxane-containing segments include alkyl, fluoroalkyl,
and chloroalkyl siloxanes. More specifically, dimethyl siloxanes
and polydimethylsiloxane materials are useful. Mixtures of any of
the above may be used. In certain embodiments, the
"CO.sub.2-philic" segment may be covalently linked to the
"CO.sub.2-phobic" segment.
[0029] For the purposes of the invention, one cannot employ a
CO.sub.2-phobic segment alone as the surfactant since it would not
be sufficiently soluble in CO.sub.2. One can however use a
CO.sub.2-philic segment solely as a surfactant.
[0030] Surfactants that are suitable for the invention may be in
the form of, for example, homo, random, block (e.g., di-block,
tri-block, or multi-block), blocky (those from step growth
polymerization), and star homopolymers, copolymers, and
co-oligomers. Exemplary homopolymers include, but are not limited
to, poly(1,1'-dihydroperfluorooctyl acrylate) ("PFOA"),
poly(1,1'-dihydro-perfluorooctyl methacrylate) ("PFOMA"),
poly(2-(N-ethylperfluorooctane-sulfonamido) ethyl methacrylate)
("PEtFOSEMA"), and poly(2-(N-ethylperfluorooctane sulfonamido)
ethyl acrylate) ("PEtFOSEA"). Exemplary block copolymers include,
but are not limited to, polystyrene-b-poly(1,1-dihydroperfluoroo-
ctyl acrylate), polymethyl
methacrylate-b-poly(1,1-dihydroperfluorooctyl methacrylate),
poly(2-(dimethylamino)ethyl methacrylate)-b-poly(1,1-dihyd-
roperfluorooctyl methacrylate), and a diblock copolymer of
poly(2-hydroxyethyl methacrylate) and
poly(1,1-dihydroperfluorooctyl methacrylate). Statistical
copolymers of poly(1,1-dihydroperfluorooctyl acrylate) and
polystyrene, along with poly(1,1-dihydroperfluorooctyl
methacrylate) and poly(2-hydroxyethyl methacrylate) can also be
used. A preferred block copolymer is
polystyrene-b-poly(1,1'-dihydroperfluoroocty- l acrylate)
("PS-b-PFOA"). Graft copolymers may be also be used and include,
for example, poly(styrene-g-dimethylsiloxane), poly(methyl
acrylate-g-1,1'dihydroperfluorooctyl methacrylate), and
poly(1,1'-dihydroperfluorooctyl acrylate-g-styrene). For the
purposes of the invention, multiple surfactants may be employed in
the invention, if so desired.
[0031] Although a number of examples of surfactants listed herein
are in the form of block, random, or graft copolymers, it should be
appreciated that other copolymers that are not block, random, or
graft may be used.
[0032] If employed, the amount of surfactant that is used in the
reaction mixture may be selected from various values. Preferably,
the fluid mixture comprises from about 0.01 to about 30 percent by
weight of the surfactant, and more preferably from about 1 to about
20 percent by weight. It should be appreciated that this amount
depends on several factors including the stability of the
surfactant and desired end product. In a preferred embodiment, the
surfactant should be selected such that it does not react with the
reactive functional polymer.
[0033] The reaction mixture may also comprise components in
addition to those described above. Exemplary components include,
but are not limited to, polymer modifier, water, rheology
modifiers, plasticizing agents, antibacterial agents, flame
retardants, and viscosity reduction modifiers. Co-solvents and
co-surfactants may also be optionally employed. These components
may be used if they do not react with the reactive functional
polymer.
[0034] The methods of the invention may take place using known
equipment. For example, the polymerization reactions may be carried
out either batchwise, continuously, or semi-continuously, in
appropriately designed reaction vessels or cells. Additional
features may be employed such as, for example, agitation devices
(e.g., a paddle stirrer or impeller stirrer) and heaters (e.g., a
heating furnace, heating rods, or a heating rope). Typically, the
initiator, monomer or monomers, surfactants, carbon dioxide, and
other optional ingredients are added to the vessel or cell and the
reaction begins by heating the reaction vessel or cell to a
temperature above about 30.degree. C. (preferably between about
55.degree. C. and about 75.degree. C. The temperature of the
reaction may depend on various factors such as, for example, the
type of initiator employed. Preferably, the mixture is allowed to
polymerize for between about 4 h and 24 h and preferably is stirred
as the reaction proceeds. At the conclusion of the reaction, the
polymer can be collected by methods known to one skilled in the art
such as, without limitation, venting of the carbon dioxide, or by
fractionation. Preferably, the surfactant is fractionated from the
carbon dioxide and polymer by supercritical fluid extraction, and
thus is able to be reused if so desired. After separation, the
polymer can be collected by conventional means. In addition, the
polymers of the present invention may be retained in the carbon
dioxide, dissolved in a separate solvent evaporate, and applied
(e.g., sprayed) to a substrate surface. After the carbon dioxide
and solvent evaporate, the polymer forms a coating on the surface
of the substrate.
[0035] As alluded to in greater detail herein, composite particles
containing two or more distinct polymers, copolymers, etc. can be
made in accordance with the invention, and usually encompasses
forming these materials in two distinct polymerization stages
utilizing, for example, conditions set forth herein.
[0036] In another embodiment, the invention may optionally further
include the step of reacting the polymer containing reactive
functionality with a second polymer containing reactive
functionality such that the polymers containing reactive
functionality crosslink, i.e., chemically crosslink. Examples of
second polymers containing reactive functionality include, without
limitation, ones that contain a nucleophilic functional group, such
as alcohols (e.g., poly(hydroxyethyl acrylate) and
poly(hydroxyethyl methacrylate)), primary and secondary amines
(e.g. poly(2-aminoethyl methacrylate),
poly(2-(tert-butylamino)ethyl methacrylate), and
poly(2-(iso-propylamino)ethyl styrene)), and alkyl halides (e.g.
poly(2-chloroethyl methacrylate). In a specific embodiment, the
polymer containing reactive functionality may be applied with the
second polymer containing reactive functionality to the substrate
described herein such that these polymers become crosslinked.
Moreover, in another embodiment, the polymer contains isocyanate
reactive functionality and the second polymer contains an alcohol
such that a urethane linkage is present between the two polymers.
The crosslinking of the these polymers can be carried out using
techniques that are known to one skilled in the art, and can be
monitored by known means such as, for example, FTIR
spectroscopy.
[0037] In another embodiment, the reactive functional polymer may
react with a molecule containing a reactive functional group.
Examples of such molecules include those containing a nucleophilic
functional group such as, without limitation, an alcohol (e.g.
methanol and octanol), a primary amine (e.g. ethylamine and
1-decylamine), a secondary amine (e.g. dimethylamine, diethylamine,
and pyrrolidine), an alkyl halide (e.g. 1-chloropropane), and an
amino acid (e.g. alanine and lysine). Other molecules that can be
reacted with the reactive functional polymer, include, but are not
limited to, peptides, enzymes (e.g. lipase and esterase), and
proteins (e.g. insulin and bovine serum albumin). Combinations
thereof can also be employed.
[0038] Optionally, the method of the invention may include other
steps. For example, in one embodiment, the method may include
separating the polymer containing reactive functionality from the
reaction mixture. Preferably, the method further comprises applying
the polymer containing reactive functionality to a substrate.
Techniques for separating the polymer and applying to a substrate
are known in the art and are described, for example, in U.S. Pat.
No. 5,863,612 to DeSimone et al., the disclosure of which is
incorporated herein by reference in its entirety. Examples of
methods for separating the polymer include, without limitation,
boiling off the carbon dioxide and leaving the polymer behind, and
precipitation of the polymer into a non-solvent either by
introducing a non-solvent to the reactor or the transfer of the
reactor contents to another vessel containing a non-solvent for the
polymer. In one embodiment, the separation and application steps
may be carried out together and include, as an example, passing
(e.g., spraying or spray-drying) a solution containing the polymer
through an orifice to form particles, powder coatings, fibers, and
other coatings on the substrates. A wide variety of substrates may
be employed such as, without limitation, metals, organic polymers,
inorganic polymers, textiles, and composites thereof. These
application techniques are demonstrated for liquid and
supercritical solutions.
[0039] Optionally, the polymer containing reactive functionality
may be applied with a second polymer having reactive functionality
to the substrate, and the polymers may thereafter be crosslinked by
known techniques to form a crosslinked polymer coating on the
substrate.
[0040] In another embodiment in which the polymer is in the form of
a solid particle, the method of the invention may further include
the step of polymerizing at least one additional monomer having
ethylenic unsaturation in the presence of the solid particle to
form a second polymer that becomes attached (either physically or
chemically) to the solid particle to form a composite particle.
Various olefinically unsaturated monomers can be used including,
without limitation, those described hereinabove. Copolymers,
terpolymers, and the like can also be formed in which case more
than one monomer would be polymerized.
[0041] The following examples are intended to illustrate the
invention and are not intended as a limitation thereon. In the
examples, isocyanatoethyl methacylate (IEM),
azobis(isobutyronitrile) (AIBN), glycidyl methacrylate (GMA),
hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA) and
styrene (STY) were provided by Aldrich of St. Louis, Mo., with the
AIBN being recrystallized from methanol. Styrene and MMA were
deinhibited by passage through an alumina column made commercially
available by Aldrich. Carbon dioxide was provided by Air Products
and Chemicals, Inc. of Allentown, Pa. Tetrahydrofuran (THF) was
made commercially available by Mallinckrodt of Paris, Ky. and HPLC
grade THF was made commercially available by Allied Signal of
Muskegon, Mich. PS-b-PFOA surfactant (4.2 K/37.5 K) was synthesized
by Hiroshi Shiho.
[0042] A high pressure variable volume reactor was employed in the
examples. The reactor has a maximum volume of 39 mL and is a HiP
pressure generator modified with three ports and a sapphire window
on the end for visual observations. The window and ports of the
reactor are described in detail in Lemert, R. et al. J. Supercrit.
Fluids 1990, 4, 186. One of the ports contains a thermocouple which
is used to monitor the reactor temperature, another port is
connected to a 2-way valve used for second-stage monomer addition
and for venting, and the third port is connected to a 3-way valve.
One side of the 3-way valve leads to a rupture disk housing and
pressure transducer and the other side is used for the carbon
dioxide delivery line. The reactor is equipped with a magnetic
cross-shaped stir bar for magnetic stirring and is wrapped with
electric heating rope for heating. The reactor is horizontal and
tilted such that the stir bar remains against the sapphire window
in order to observe whether or not stirring is taking place.
[0043] A general synthesis procedure that was used in the examples
is as follows. Following the addition of surfactant and initiator
to the variable volume reactor through the sapphire window, the
reactor was sealed and purged with argon (Ar) for 15 min. The
first-stage monomer(s) was degassed with Ar for 15 min and then
injected into the reactor under Ar with a syringe through one of
the reactor ports. After the reactor was purged another minute with
Ar, the carbon dioxide delivery line was purged with carbon dioxide
and the reactor was pressurized with carbon dioxide to
approximately 70 bar using an ISCO model 260D automatic syringe
pump. The reaction mixture was stirred with a magnetic stir bar and
heated to 65.degree. C. with electric heating rope. Once the
temperature reached 63.degree. C., the reactor was pressurized with
carbon dioxide to the final reaction pressure. Initially, the
reaction mixture appeared clear and colorless upon reaching the
reaction temperature and pressure then progressed from cloudy white
to milky white.
[0044] In the event that a second-stage polymerization was
employed, the second stage monomer(s) with initiator solution was
prepared, filtered through a 0.2 .mu.m syringe filter and stored in
an ice bath. Carbon dioxide was added to maintain the reaction
pressure while the reactor volume was increased. The HPLC pump was
primed with HPLC grade THF to remove air and purged with
second-stage monomer(s)/initiator solution. The pump was
pressurized to the reaction pressure with second stage
monomer/initiator solution and run at 1 mL/min until the desired
amount was injected. During the addition, the reactor pressure was
maintained by manually increasing the reactor volume. The actual
amount of second-stage solution added was determined by weighing
the solution flask before and after the injection. Immediately
following the addition, carbon dioxide was injected into the
reactor to clear the injection valve and line of second stage
monomer(s)/initiator solution and the reactor volume was increased
to maintain the reaction pressure. The dispersion remained stable
and milky white in appearance during the entire reaction period,
with little if any polymer precipitation or settling even when the
stirring was momentarily stopped. After the second-stage reaction
time of 24 hr, the reactor was rapidly cooled to 25.degree. C. in
an ice bath. Thereafter, the carbon dioxide was slowly vented into
hexane. Dry polymer powder was recovered from the reactor and the
remaining polymer was recovered with THF. Polymer was dried under
vacuum overnight and the yield was determined gravimetrically.
EXAMPLE 1
Homopolymerization of Isocyanatoethyl Methacrylate
[0045] A variable volume reactor having an initial size of 11 mL
was purged with argon and heated to 100.degree. C. for an hour and
then cooled prior to the addition of reactants. Through a sapphire
window opening was added 0.1 g of PS-b-PFOA (4.2 K/37.5 K) and AIBN
having a concentration of 0.07 M in IEM to the reactor and the
reactor was thereafter sealed and purged with argon for 15 minutes.
IEM in the amount of 0.73 mL was added in the manner set forth
above. The reaction pressure was 365 bar. The polymerization
proceeded for at least 20 h. The IEM was successfully polymerized
to form poly(isocyanatoethyl methacrylate) (PIEM).
EXAMPLE 2
Polymerization of Styrene in the Presence of PIEM
[0046] Styrene was polymerized in the presence of the PIEM
particles formed in Example 1 to form composite particles.
Following the polymerization in Example 1, the reactor volume was
increased at constant pressure to 17 mL. Thereafter, 1.6 g of a
solution of 0.11 M AIBN in STY was added to the reactor employed in
Example 1. The final volume of the system was 19 mL. The pressure
employed during this reaction was 360 bar carbon dioxide. The
target mol ratio percent of PIEM to polystyrene (PS) was 20:80.
EXAMPLE 3
Copolymerized Composite Polymer Particle
[0047] A copolymerized composite polymer particle was formed
according to the below procedure. In the reactor described in
Example, 0.6 mL containing IEM and methyl methacrylate (MMA) in a
20:80 mol percent ratio respectively were copolymerized having an
initial volume of 9 mL using 0.1 g of the same surfactant. AIBN
(0.03 M) was used as initiator. The reaction pressure was 365 bar.
After particles of copolymerized PIEM and PMMA were formed, the
reactor volume was increased at constant pressure to 17 mL. HEMA
and styrene (2 gms) in a 5:95 mol percent ratio respectively were
injected into the reactor and copolymerized using 0.11 M AIBN as
the initiator. The volume during addition was determined to be 17
mL. The reaction pressure was 360 bar. The final volume of the
system was 19 mL. The target mol ratio percent of IEM:PMMA:PHEM:PS
was 4:16:4:76.
EXAMPLE 4
Homopolymerization of Glycidyl Methacrylate
[0048] Glycidyl methacrylate (GMA) was polymerized using the
reactor described in Example 1. To the reactor was added 1.4 mL of
GMA, the reactor having an initial volume of 10 mL. The pressure of
carbon dioxide was 390 bar. 0.44 g of PS-b-PFOA (4.2 K/19.7 K) and
AIBN having a concentration of 0.06 M in the GMA were added to the
reactor through a sapphire window opening and the reactor was
thereafter sealed. The reaction proceeded for at least 20 h such
that the formation of PGMA occurred.
EXAMPLE 5
Polymerization of Styrene in the Presence of PGMA
[0049] STY was polymerized in the presence of the PGMA particles
formed in Example 5 to form composite particles. Following the
polymerization of 0.7 mL of GMA with 0.22 g of surfactant in the
reactor with a volume of 12 mL according to Example 4, the reactor
volume was increased at constant pressure to 17 mL. To the reactor
employed in Example 1 was added 1.6 g of STY in a volume of 17 mL
using 0.22 g of surfactant. AIBN was used as initiator at a
concentration of 0.11 M. The final volume of the system was 19 mL.
The reaction pressure was 390 bar. The reaction proceeded for at
least 20 h. The target mol ratio percent of PGMA to PS was
20:80.
EXAMPLE 6
Copolymerized Composite Polymer Particle
[0050] A copolymerized composite polymer particle was formed
according to the below procedure. GMA and MMA (0.58 mL) in a 20:80
mol percent ratio respectively were copolymerized in the reactor
described in Example 1 having an initial volume of 11 mL using 0.12
g of PS-b-PFOA (4.2 K/19.7 K) as surfactant. AIBN (0.03 M) was used
as initiator. The reaction pressure was 390 bar. Particles of
copolymerized PIEM and PMMA were formed. The reactor volume was
increased to 17 mL at a constant pressure. Using 0.11 M AIBN as
initiator, 1.6 gms of STY was thereafter polymerized. The volume
during addition was determined to be 17 mL. The final volume of the
system was 19 mL. The second stage pressure was 370 bar. The
reaction proceeded for 20 h. The target mol ratio percent of
PGMA:PMMA:PS was 4:16:80.
[0051] In the specification, and examples there have been disclosed
typical preferred embodiments of the invention and, although
specific terms are employed, they are used in a generic and
descriptive sense only and not for the purposes of limitation, the
scope of the invention being set forth in the following claims.
* * * * *